1. Field Of The Invention
The present invention relates generally to boom assembly structures and, more particularly, to telescopic boom assemblies which are mountable to a utility vehicle, construction vehicle or the like. Specifically, the present invention relates to such telescopic boom assemblies which have high dielectric properties.
2. Description Of The Prior Art
Boom assemblies of various types and designs are often employed on cranes and other types of construction or utility vehicles to extend a work tool of some sort mounted on the very end of the boom to positions above and about the vehicle position. A particularly useful example includes utility or construction vehicles having boom assemblies wherein a bucket or other carrier is mounted at the end of the boom assembly. The bucket or carrier is adapted to allow an individual to stand or sit therein for the purpose of working at stations above the ground level of the utility vehicle, such as telephone or utility poles.
Prior boom assembly designs have included pivotal arm arrangements such as disclosed in U.S. Pat. Nos. 3,947,191 and 3,958,377. While these patents disclose nonconductive fiberglass boom constructions, they are limited to pivotal type designs. Other more complicated boom assembly arrangements commonly include telescopic booms whereby a plurality of boom sections are telescopically disposed relative to each other and are extended section by section. Examples of such telescopic booms includes U.S. Pat. Nos. 4,327,533, 4,337,601, 4,478,014, 4,258,853 and 3,845,596. The advantage of such telescoping design is that a greater reach or extension can be obtained. As can be seen from these references, a wide variety of telescopic boom arrangements are known and are available for adaptation to a multitude of purposes. The telescopic boom arrangement is generally preferred in that it is much more compact when in its retracted position on the utility vehicle for traveling purposes.
A common problem with all such telescopic boom assemblies is that if they are to achieve the purpose of providing a substantially extended reach with the operator bucket at the end thereof, they must be constructed from strong materials to provide sufficient strength to carry the axial load as the arms thereof extend outwardly and retract back as well as to carry the depending load at the end of the boom assembly in a fully extended position. Consequently, such boom assemblies have generally been constructed from steel or other similar metal components to provide the necessary structural strength for repeated use. A significant disadvantage with such arrangements is that they are highly conductive thereby placing the worker loacated in the end bucket in jeopardy of receiving electrical shocks in the event the worker is required to work around high voltage items such as utility poles. Therefore, it would be highly desirable to have a telescopic boom assembly with high electrical insulative properties so as to provide a substantial safety factor for a worker positioned at the end of the boom assembly.